Peter Michael Doubilet MD, PhD, Presenter: Nothing to Disclose

Carol Beer Benson MD, Abstract Co-Author: Nothing to Disclose

To determine the outcome of pregnancies with a slow embryonic heart rate at 6.0-7.0 weeks gestation and a normal heart rate on a follow-up scan performed by 8.0 weeks gestation.

We identified all singleton pregnancies scanned at our institution since 1998 with an embryonic heart rate measured on a 6.0-7.0 week sonogram. Heart rate was classified as slow if =100 bpm at =120 bpm at 6.3-7.0 weeks; and borderline if between these values. Cases were excluded from analysis if the pregnancy was lost to follow-up before the end of the first trimester.

The rates of first trimester loss were 60.6% in pregnancies with slow heart rates at 6.0-7.0 weeks (188 losses in 310 pregnancies), 17.4% in those with borderline heart rates (103/593), and 9.1% in those with normal heart rates (186/2034). There were 59 pregnancies with a slow heart rate at 6.0-7.0 weeks in which the heart rate was normal on a follow-up scan by 8.0 weeks. Fifteen of these (25.4%) resulted in first trimester loss. This loss rate was significantly higher than the loss rate of 7.2% (28/390) in pregnancies with a normal heart rate at 6.0-7.0 weeks followed by a normal heart rate by 8.0 weeks (p<.0001, Fisher exact test). Pregnancies with a borderline early heart rate followed by a normal heart rate had a loss rate of 7.6% (9/118), similar to those with normal early heart rates followed by normal heart rates (p=.84).

When a slow embryonic heart rate is detected at 6.0-7.0 weeks, the likelihood of subsequent demise remains elevated even if the heart rate is normal on a follow-up scan. In such cases, continued sonographic follow-up through the end of the first trimester is warranted.

Doubilet, P, Benson, C, Outcome of Pregnancies with a Slow Embryonic Heart Rate at 6-7 Weeks Gestation and Normal Heart Rate on a Follow-up Scan by 8 Weeks.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4403518.html